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Discussion Starter · #1 ·
Help Needed. Having trouble getting firm brake pedal after complete system replacement of 1963 Spider brake system . Everything in complete system is new. Discs in front and .75 master cylinder. Have bled system with vacuum and good old fashion way several times. Get clear fluid at all wheels. Using silicone fluid. Pedal is very soft and goes almost to floor. Suggestions to fix would be greatly appreciated.
Franklin
 

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But Mad North-Northwest
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Did you try bleeding at the master? Crack a fitting slightly, push pedal down, tighten fitting, release pedal. Do this a few times for each of the outlets. If you installed the master dry then it can be tough to get all the air out by bleeding at the wheels.

Personally I think silicone fluid is a bad idea, but it's your car. It's known to cause spongy brake feel but sounds like your issue is more than could be explained by just the fluid. Some relevant technical notes at Moss here:

Tech Article: Brake Fluid
 

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From my own experiences with this system, the seals in the master do not seem to like silicone fluid, and you may never get a nice pedal feel. Getting the silicone OUT of the system is another big problem. When I went through this exercise on a '65 Spider Veloce, I ended up rebuilding or replacing everything except the lines over the next two years. I've stayed away from synthetic or silicone with these ever since, using ATE Blue or Gold, with no issues, ever since.
As this system has no vacuum booster, when NEW it had a spongy pedal with the 3/4" master.
Many used the 1" master which requires more pedal effort, but the pedal feels firm. Just replacing the rubber flex lines with braded stainless steel is not enough to eliminate the spongy pedal.
 

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Are your brake shoes adjusted correctly? If you have never done it before it can be a sketch adventure and can leave the brakes spongy too.
 

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But Mad North-Northwest
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Well, that would surprise me, since silicone oil is generally very compatible with almost all types of rubber. But I've never personally tried it and you have, Gordon, so maybe there's some weird interaction.

Note that "synthetic" doesn't mean anything with regards to brake fluid: it's just a marketing term. Several brands (Valvoline, and I think Castrol) sell their DOT 3 or DOT 4 as "synthetic", but as long as it's DOT 3 or 4 it's glycol and no different from any other stuff. The DOT 5 is the silicone.
 

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Well to throw a cat among the pigeons here, we run silicone in everything we restore, if we have to touch the brake system, we flush & rebuild it completely with new washers & Bel-Ray DOT 5 which our local Speedyquip Shop keeps in stock for the motor cycle guys.

Yes silicone gives you a slightly spongy pedal feel - but it's just that, slightly spongy, basically the same feel as with normal DOT 3 or 4 where you want to "bleed it just once more".

We're in the process of rebuilding the brakes on Dad's 1930 Triumph Super 7 Tourer which has been running silicone in the original Lockheed master cylinder & wheel cylinders for the past 30+ years. Been trouble free for years, even after standing for 2 years at a time, still has good brakes, but the washer in the MC finally lost its 'edge' so to speak, hence the rebuild. Takes the same 1" washers as the Giulietta's so no issues there.

We swapped our '68 Nissan Silvia CSP 311 Coupe over to Bel-Ray DOT 5 before a big Tour 5 or 6 years ago - no issues, did the clutch slave last year. We have 4 Giulietta's running on silicone at the moment.

Franklin you have air in the system, or a bad Master Cylinder - these are the only things that will put the pedal to the floor, (assuming there are no leaks anywhere)

One caution with silicone fluid - it aerates really easily, so push the brake pedal slowly when bleeding. If you pump fast & hard, it will cause the fluid to mix with the air in the system and you will need to leave it overnight before bleeding it again.

Also you need to pull a vacuum at the mouth of the reservoir to lift the air out of the MC - do a visual check and jack up the back of the car to make sure that the MC is nose-down to get rid of that last bubble at the top of the bigger end.

Ciao
Greig
 

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Discussion Starter · #7 ·
Thank you to those of you that took the time to reply. I now have a few additional things to try. This will be my Sat. project.
Franklin
 

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I'm sold on power brake bleeders that run off a small compressor. If you don't have one, your friends at a local garage or gas station will let you borrow theirs and show you how to use it in 3 minutes. You will only need it for like an hour or so and they are wonderful. I let my reservoir get too low once while manually bleeding and the bleeder saved me a lot of time and crawling around to get it back to normal and the air out of the master. Bench bleeding a master after rebuild is always a SOP but the power bleeder saves that.

Another time tested method is good old gravity. Open the LR first and let it flow through a clear tube and go about your business washing the dog or mowing the grass. start at RR and so on. It takes anywhere from 15-30 minutes on each wheel. Don't touch the brake pedal. If there is air you will see bubbles the size of a pea or on a sight glass on a carpenter's level not foam.

I know an ancient restorer ( he is not the cars) who uses this method on every car he ever works on and has success everytime..

It sounds like you have tried all the above .. it must be the DOT5 that is giving you the sponginess. I never used it because I don't spill my brake fluid or wash it off with a splash of water, and use ATE Blue (NLA) and Gold which is good for many seasons between bleeds. It's what it is for you unless you want to start all over with rebuilding everything.
 

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Yup. Agree. Been there and done that. Never again.


"It sounds like you have tried all the above .. it must be the DOT5 that is giving you the sponginess. I never used it because I don't spill my brake fluid or wash it off with a splash of water, and use ATE Blue (NLA) and Gold which is good for many seasons between bleeds. It's what it is for you unless you want to start all over with rebuilding everything."

Just like my first post Uncle...
 

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I'm just going to throw this out there. I have every kind of brake bleeding equipment made. I have found a new product which is a reverse brake bleeder by Phoenix Systems. It was originally made for motorcycles, but on almost every car this tool works great. Instead of pushing fluid out to the bleeders, you push fluid upwards into the reservoir where air bubbles belong at the top.

I'm in the repair and restoration business and I do support this product. Check it out.
 

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I also use dot 5 and the gravity bleed method. Brakes work great. Never had a problem with dot 5 and continue to use it in several vehicles.
 

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You should verify the bore diameter of the rear wheel cylinders is correct, Disc brake cars use a different size rear wheel cylinder. that can contribute to the pedal travel.
DB
 

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Silicone fluid

We've just finished bleeding the original Lockheed master cylinder & wheel cylinders on Dad's '30 Triumph Super 7. Gently pumped new Bel Ray DOT 5 Silicone fluid through the system, let it stand overnight & re-bleed the next day. Perfect pedal pressure.

Same as all our Giulietta's

Aye
Greig
 

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Dad bought it in April '62, he's had it 53 years now, it's a keeper. He & Mum are on a Pre-40's Tour with it this weekend.

It's the sister car to the one Ron Hollis has in Knysna

Cheers
Greig
 

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I just went through this with a '61 Giulietta, and it turned about to be a bad master cylinder (new). Where did you get your MC?

Don
 

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Discussion Starter · #19 ·
My master cylinder was new and tested OK. Removed outlet line and replaced with plug. Pedal was rock hard with no travel. My current thinking is that 3/4 master had inadequate volume. Have sent old 1" out to be sleeved and rebuilt. Someone mentioned checking rear wheel cylinders for correct size-they are .70 as they should be with front discs.
Franklin
 

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Pedal will require more effort, but 1" or even 1 &1/8 " was used with this system in racing back-in-the-day. On my own '65, I just swapped our Giulietta 2 shoe front drums with race linings, and used a 1" cylinder. The car had (has) an adjustable bias valve, and once set up this system served perfectly on the track for years. The 2 shoe radially finned front drums were lighter than the disc set up. Pedal was FIRM with no sponginess. NO brake fade ever. Minimal lining wear ever. Essentially -0- maintenance.
Alfa was ALWAYS experimenting with what might be "better" brakes, and unlike Ferrari, had the best brakes on the track. Some of Alfa's systems were works-in-progress, like the early unboosted front disc, rear drum systems, but they were always more than adequate for the weight of the cars at speed.
Just my opinion as usual, from my own experiences.
 
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